1. Field of the Invention
This disclosure relates generally to an outboard propulsion system for a vessel. More particularly, this disclosure relates to an outboard propulsion system wherein a mechanical connection between the engine and the propeller is not required and wherein the operation of each component of the system may be optimized.
2. Description of the Prior Art
The usage of hybrid propulsion systems has been growing in the last years as a consequence of fuel savings needs, among other reasons. This type of system brings great advantage for the marine industry. The pioneer versions of this type of system are emerging in the industry.
One of the main issues considered as an obstacle with regard to this type of system in the marine industry is precisely their installation, because it turns out to be a very expensive and time consuming task. Moreover, the installation is based on a high number of independent components or devices, which are installed in different locations, depending on the particular characteristics of the vessel or boat. This means that the installation process cannot be standardized for each boat; rather, it needs to be customized, making the installation and maintenance more complex and highly dependent on specialized professionals.
A conventional marine hybrid system typically includes one or more generator units coupled to one or more motor drives. The motor drive(s) changes the boat speed as well as controls the propulsion motor(s). A generator unit is formed by a gas or diesel engine mechanically linked to an AC or DC generator. Other types of generators that could be used, either individually or in combination with an AC or DC generator include: solar panels, batteries, fuel cells, or other electrical generation technologies. The generators can be cooled using water or air, and usually their work speed is fixed or controlled depending on the nominal frequency of the current which powers them.
The motor drive is used to change the speed or torque of the motor. The motor drive controls and monitors a set of parameters in the motor(s) and/or generator(s). The motor drive, or inverter, can be cooled by water or air. Water is typically used in the marine applications since water is available in large quantities.
The propulsion motors can be AC or DC. The main differences between AC and DC motors are their size and weight for a given power capability. AC motors weigh less and are smaller in size than DC motors; however, their electronic systems are more complex than that of DC motors.
The devices mentioned above, meaning the motor drive, propulsion motor, and generator units, typically have a protection panel as well as a general control device. This general control device monitors all of the parameters and variables of the complete system. It also contains the algorithms that make it possible to generate electricity within tie values and operation points that allow a higher efficiency of the engine. In other words, the general control device is in charge of optimizing the generation of electricity based on demand. This device also includes algorithms for fault detection, and can perform diagnostics if one or more of the devices fails or displays an inappropriate value.
Determining the position of the devices as well as installing them is a time intensive and costly process, which is not done properly, may result in a high number of system failures. Moreover, if the devices are to be water-cooled, it is also necessary to position and install a cooling system with all of the devices involved.
Usually a marine propulsion system has a supervising device, or human machine interface, for the selection and configuration of the system controlled by the captain or person in charge of the boat. The captain can observe the parameters and configure the system according to the maneuver to be performed by the boat with this device.
In the outboard marine propulsion system industry, there are hybrid propulsion systems that have a mechanical connection between the engine and the propeller. These systems do not enable optimization of the operation of their subcomponents, or positioning and operation of their engine in a horizontal position. Furthermore, installation of these systems is costly and requires the skill of specialized technicians.